Generally, the semiconductor manufacturing industry involves highly complex techniques for integrating circuits into semiconductor materials. Due to the large scale of circuit integration and the decreasing size of semiconductor devices, the semiconductor manufacturing process is prone to processing defects. Semiconductor defects may include structural flaws, residual process material and other surface contamination, which occur during the production of semiconductor wafers. Defects can be introduced to a wafer at any process step in wafer production. For example, a particle defect may originate from contamination during a deposition process or it may be introduced to the wafer due to exposure during a wafer transfer from one process chamber to another. As another example, a scratch defect may occur due to abrasive polishing during a chemical mechanical planarization process, or it may occur due to faulty cleaning process or it may occur from operator error during wafer handing. Since defects can have a similar appearance but originate from different process steps, it can be difficult to find root causes of the defects, such as a faulty process.
To help detect and locate defects, a class of instruments called inspection tools is used. Inspection tools inspect the wafers at various critical points between process steps in wafer production. Such instruments scan wafer surfaces using a variety of techniques and detect and record the location of anomalies. Typically, these techniques involve directing a light or electron beam towards the surface of the semiconductor where the defect is, and detecting the resultant light reflected off or electrons emitted from the sample. The reflected light or emitted electrons may then be used to generate a target image of the surface of the semiconductor. In some typical inspection processes, differences between the target image and a reference image (which is known to contain no defects) are determined and, when the differences are above a predetermined threshold, it may be determined that a defect exists. In other typical inspection processes, similar semiconductor device areas are compared against each other and the detected feature differences between device areas are identified as potential defects.
To obtain specific information about a located defect or any other feature on a semiconductor substrate, additional techniques are typically employed. Examples of such specific information include the composition, size, and density of each defect. One category of techniques used to measure such information is x-ray spectroscopy, which includes X-ray fluorescence testing and X-ray micrography. Unfortunately, X-ray spectroscopy has certain inherent characteristics that effect the accuracy of measurements. For example, the high energy electron beam required to cause X-rays to emanate from a semiconductor sample cause X-rays to emanate from regions that extend beyond the specific defect being reviewed. The resulting data therefore does not reflect accurately upon the defect since data relating to areas surrounding the defect is also included. Since testing procedures are an integral and significant part of the manufacturing process, a more accurate X-ray review process would be desirable.